Gaseous electric discharge lamp device



July z3, 1935. H, KREFFT 2,009,196-

GASEOUS ELECTRIC DISCHARGE LAMP DEVICE Filed D eo. 13, 1952 INVENTOR Patented July 23, 1935 UNITED STATES PAT. OFFIC Hermann Kreit, Berlin-Schmargendorf, Germany, assignor to General Electric Company, a corporation of New York Application )December 13, 1932, Serial No. 647,021 In Germany December 14, 193i l Claim. (Cl. 176-122) The present invention relates to gaseous electric discharge lamp devices generally and more particularly the invention relates to such devices the gaseous atmosphere of which comprises a metal vapor similar to those disclosed in copending application Serial No. 609,547, filed May 5, 1932, and being the application of vMarcello Pirani, Hans Ewest, and Karl Becker.

The application referred to above discloses a method of obtaining greater operating stability and greater economy of operation of gaseous electric discharge devices having thermionic electrodes and a gaseous atmosphere comprising a metal vapor which consists in maintaining said Vapor at a pressure lower than that vapor pressure corresponding to the operating temperature of the-device. The means proposed in the cocopending application for maintaining the desired unsaturated vapor pressure is either by restricting the quantity of vaporizable material introduced into the container of the device or by maintaining the vaporizable material at a lower temperature than that of the container of the device.

The object' of the present invention is to provide a. simple method and means for maintaining the vapor pressure of a gaseous electric discharge device at a lower pressure than the pressure corresponding' to the temperature of the part of the device surrounding the discharge path. Still further objects and advantages attaching to the device and to its use and' operation will be apparent to those skilled in the art and from the following particular description and from the appended claim.

I have discovered that the desired low vapor pressure can bemaintained in a simpler and more positive manner by making the container of the device a double walled structure, the inner wall surrounding the discharge path between the thermionic electrodes, and having a communication between the inner space and the outer space of said container. The gas and vapor pressure is thus the same in both o said spaces and as the outer wall of the container is at a lower temperature than the inner wall of the container during the operation of the device, due to the greater heat radiation from said outer wall, the vapor pressure in the whole device corresponds to the temperature of the outer wall of the container while the inner wall is maintained at a temperature sucient to keep the vaporizable material in a vaporized condition. Thus the vapor pressure in the discharge path surrounded by the inner wall will be lower t that pressure correspending to the'temperature of said inner wall during the operation of the device which gives the device a negative characteristic with consequent greater oberating stability and greater eiciency than prior devices operating with a saturated vapor pressure.

In the drawing accompanying and forming part of this specification an embodiment of my invention is illustrated in a sectional side elevational view but as such illustration is primarily for purposes of disclosure it will be understood that numerous changes in the form and details of the device may be made by those skilled in the art without departure from the broad spirit and scope of the invention.

Referring to the drawing the new and novel gaseous electric discharge device comprises an elongated container having two walls 3 and 4. Electrodes 5 and 6 are sealed into said container and are located in that part of said container surrounded by said Wall 4. Said electrodes 5 ,and 6 are of the self-heating, sintered, mixed metal and oxide type, known in the art as Pirani electrodes, and are electron emitting when heated. 'An opening or vent 'i is provided in saidl wall and the gaseous atmosphere in said container thus has free access to all parts of said container 3, d. The gaseous atmosphere in said container 3, l comprises a mixture of a rare gas, such as argon, krypton, neon, etc., and the vapor of a difcultly vaporizable metal, such as alkali metals, magnesium, cadmium, or zinc. I nd it advantageous to place the diiiicultly vaporizable material on the inner wall 4 of said container 3, l.

When the above described device is first started into operation the electric `discharge is conducted between said electrodes 5 and by the rare gas constituent of the gaseous mixture and the spectrum of the light emitted is that of the rare gas. 'Ihe heat of the gaseous electric discharge quickly raises the temperature of the inner wall d and the vaporizable metal located thereon to the temperature at which said metal is vaporize-d. The spectrum of the light then emitted by the electric discharge is that characteristic of such mixtures. l

During the operation of the device the outer wall 3 is-at a lower temperature than the inner wall i as the radiation of heat from said wail 3 is greater than that from said wall l, consequently the vapor pressure in the device corresponds to the temperature of said cuter wall s and this pressure is lower than that pressure corresponding to the temperature oi the inner wall t surrounding the discharge path between said electrodes 5 and 6. The vapor is thus at an unsaturated pressure in the discharge path and the discharge has a negative characteristic.

The device operating with an unsaturated vapor pressure is thus more' eilicient and has a greater operating stability than prior devices operating with a saturated vapor pressure in the discharge Path.

A particular advantage of this type of container over the single walled container of the device disclosed in the application referred to above is that it is practical to use diiiicultly vaporizable metals, such as the alkali metals, magnesium, cadmium, sodium, and zinc as the vaporizable material, since the radiation of heat from the inner wall of the container is reduced to aminimum so that said inner wall is at a temperature sufficient to maintain such metals in a vaporized state during the operation of the device. The

new and novel gaseous electric discharge device is particularly useful in connection with high pressure electric discharges in mercury vapor.

What I claim as new and desire to secure by Letters Patent of the United States, is:-

The method of operating an electric discharge device comprising a double walled container, electrodes sealed therein, the inner Wall thereof being perforated and enclosing said electrodes and the discharge path between said electrodes, a gaseous atmosphere therein including a 'metal vapor which consists in maintaining the vapor pressure in the device at a lower pressure than that corresponding to thetemperature of vthe inner wall of said container surrounding the discharge path between said electrodes whereby the vapor pressure in the discharge path is unsaturated. 

